In known engines of this type, the assembly or replacement of the calibrated register both during engine production and during the life of the engine itself if a long and relatively complex operation. For example, with reference to FIGS. 1 and 2 which show perspective views of a known desmodromic cylinder head 9 of a four-stroke internal combustion engine, said operation involves removing a side cover 1, extracting the pin 2 on which the rocker 3 for opening the valve 4 is mounted so as to be able to extract the rocker (with its spacer washer 8) from the cylinder head 9 through an aperture 5 therein after removing the relative cover, not shown. Only then can the two registers 6 and 7 be removed from the stem of the valve 4 and replaced with new ones, repeating the described operations in the reverse order.
An object of the present invention is to provide a desmodromic cylinder head of the stated type which because of the particular conformation and arrangement of its parts, allows reduction both in register assembly time during production and in register adjustment time during periodic checking by the user or mechanic.
This and further objects which will be more apparent from the detailed description given hereinafter are attained by a cylinder head with desmodromic valve operation of the stated type in that the valve opening rocker is mounted with two degrees of freedom on its pin, one of these degrees of freedom relating to its ability to rotate about the pin and the other to its ability to translate along the pin, so that by utilising this second degree of freedom the rocker can be moved laterally onto or off the valve stem.
Advantageously, to the side of the rocker there is provided on its pin a spacer element to prevent undesirable lateral movement of the rocker.
Advantageously, the spacer element is a spring clip which could also be a helical spring (121) that is easily mounted on and removed from the pin.